1. Field of the Invention
The present invention relates to a relay apparatus. More particularly, the present invention relates to a relay apparatus managing a base station that is connected to a mobile station by wireless.
2. Description of the Related Art
In recent years, a wireless communication scheme called WiMAX (Worldwide Interoperability for Microwave Access) is being standardized in the IEEE (Institute of Electrical and Electronic Engineers).
In WiMAX, there are IEEE 802.16d (standardized) for non-movable subscriber stations and IEEE 802.16e (being standardized) for movable subscriber stations (to be referred to as mobile stations hereinafter).
WiMAX targeted for the latter movable mobile station supports an idle mode for the purposes of decreasing consumed power of the mobile station and decreasing wireless resources between the mobile station and the base station. A mobile station in the idle mode supplies power only to essential circuits and does not supply power to other circuits to extend battery life.
The mobile station in the idle mode does not register with a particular base station. The mobile station in the idle mode monitors a broadcast message (paging) periodically transmitted by all base stations of a paging group (=paging area) to check if there is traffic to the mobile station periodically.
When the mobile station determines that there is traffic to the own mobile station, the mobile station leaves the idle mode to go into a normal mode, and registers with a particular base station to establish a link between the mobile station and the particular base station. After establishing the link, the base station sends, to the mobile station, traffic addressed to the mobile station to realize incoming call (calling) for the mobile station.
The mobile station includes a mobile IP (MIP) client or includes a DHCP (Dynamic Host Configuration Protocol) client for performing IP (Internet Protocol) communication that is an upper layer of the IEEE 802.16e. According to the standard specification, the mobile station may include either of them.
FIG. 1 is a block diagram showing an example of a conventional network. In the figure, mobile stations 1 and 2 includes a MIP client 3 and a DHCP client 4 respectively. A gateway 5 is a relay apparatus managing a plurality of base stations 6 and 7. The gateway 5 includes a FA (Foreign Agent) 10, a DHCP relay 11 and a PC/LR (Paging Controller/Location Register) 12.
The FA 10 mediates MIP registration/reply messages (to be also referred to as MIP registration request/registration reply messages) between the mobile station including the MIP client 3 and a home agent (HA) 13. The DHCP relay 11 mediates DHCP request/acknowledge messages between the mobile station 2 including the DHCP client 4 and the DHCP server 4. The PC/LR 12 is a functional unit defined in the WiMAX standard for controlling paging and idling.
In FIG. 1, although the gateway and the base station are separated, the function of the base station and the function of the gateway may be integrated in one apparatus. Also in descriptions of embodiments of the present invention hereinafter, the function of the base station and the function of the gateway may be integrated into one apparatus.
Also, although the FA 10, the DHCP relay 11 and the PC/LR 12 are provided in one apparatus in the example shown in FIG. 1, the functions may be distributed to separated apparatuses. Also in descriptions of embodiments of the present invention hereinafter, the functions may be distributed to separated apparatuses.
The mobile station 1 in the idle mode including the MIP client 3 periodically performs MIP registration (MIP renewal process) for keeping a MIP session.
The mobile station 2 in the idle mode including the DHCP client 4 periodically performs DHCP renewal process for keeping a leased address.
At this time, since the mobile station in the idle mode does not establish an uplink connection to the base station, the mobile station needs to leave the idle mode to perform network entry process such as ranging in order to send uplink traffic necessary for performing the MIP/DHCP renewal. In the network entry process, the mobile station registers with the above-mentioned particular base station, and establishes a link between the mobile station and the particular base station.
After performing the MIP/DHCP renewal process, the mobile station returns to the idle mode immediately.
The above-mentioned process for leaving the idle mode is not a process following a call and the like by a user, but is a process periodically performed based on the standard of a control protocol of IP.
In addition, the process is not limited to MIP and DHCP. The process occurs similarly when the mobile station implements a protocol that requires periodic timer updating process.
In addition, when the mobile station implements a protocol that requires periodic timer updating process, there is a server including a timer that is an updating object in relation to the mobile station on a network. In FIG. 1, each of the HA 13 and the DHCP server 14 corresponds to the server.
By the way, a basic reason that such process is required is that the specification of IEEE 802.16e and the specification of IP are defined independently.
Japanese Laid-Open Patent Application No. 2005-253062 (Patent document 1) discloses a method in which, when there are data to be transmitted to a terminal operating in a sleep mode, a base station sends traffic information to the terminal using a TRF_IND message to change the terminal into an active mode.
In the conventional method, the mobile station implementing the protocol that requires the timer updating process needs to leave the idle mode once to go into the normal mode in order to perform the renewal process. Thus, there is a problem in that such method is disadvantageous in view of decreasing consumed power and decreasing wireless resources to be used.